Electric current inverting system



Oct. 17, 1933.

E. KERN 1,930,976 ELECTRIC CURRENT INVERTING sys-*rsu Filed Aug. 3l, 1932 2 Sheets-Sheet 1 Oct. 17, 1933. E. KERN ELECTRIC CURRENT INVERTING SYSTEM Filed Aug. 3l, 1932 2 Sheets-Sheet 2 Patented 17, `1933 y ,ELEc'rmc CURRENTINVEETING SYSTEMQK l Enetliaen;istvitzerlandfassignor to Aktie.ngesellschaft` Brown lBovini,Y & Cie.,

y voltage of a synchronousmotor"connected to such `?synchronousmotor must nrstl'be startedland l brought upY to'A operating jspe'ed and 'thereupon y and gradually decreases itsspeed and its outputy "1; Switzerland ,l

n Thisinvention relates tofthel 'controljof'sys-p terr1s`-for` convertingy direct ecurrent" into-falter? 'nating current ,by means ofselectri'c 'current rec'- tifiers of ythe gaseous"orfotvtheffmetallic vapor .arcing type andr moreparticularlyito l a protective means for systems. of such i character supplying f alternating current; circuits Knot y connected`- with f converters vof a different character or withgen-` erators. 3 'i y 13 `1 In systems for-,converting direct currentin'to Iquency of suchvoltagein theAVK alternating current output circuit are'deterrnined4 by the terminal circuit. rAlthough `such motor provides the Wave formi for the `circuitj,vthe\ "energ'yfrequired ifor system? and constitutes a'negli'gibly smallI frac`- tionof the output ofl'the'system. The voltage of the output circuit must The equalto the terminal voltageof the `-sync'zhronous motori and islde termined by the magnitude of the voltage, inthe' Vdirectjcurrent supply line, `bythe':ratioofthe supply transformerused in'the system and --by verting systemV isto beput into operation the excited' atv 'its normal operating" voltage; Such operating voltage atfthe time? of connection of the supplyl transformer to itlie'supply liner-the motor will draw excessivek current which Willi v'create a disturbance'in the system (and will' endanger the windings of the `motor. -During normal operation'ofthe systemyif a short 1 cir-L, cuit occursin the alternatingjcurrentr output circuit; the alternatingcurrent voltageis reduced` to a small value and thev` supply transformer constitutes ashort` circuitio'r the direct current supply'line so that ity becomes necessary Vto' disconnect the inverting system ,-fromthe supplyline by suitable means. At vthe time of such occurrence the .synchronous'motor operates as a generator in supplying current t0the` short circuit lpoint voltage,` so that, whenthejline ijs againl tombev putici'rcuit isdetermined byrnanswhich are au operating voltage isfirnpressed on xthewindings of the supply transformerY which' .can then 'be 3.5.?*connected with the direct current "supply line. Ifwthie synchronous motor is notexcited at thef of theunivrung system with the suppiyjnne w'oum produce adetriment'al current surgetherein. It is then necessary tof'providelfree excitation of i" for disconnecting tllensynclironous ,motor 'from f the alternating current circuit `and maintaining such motor at its normal "speed and atitsV normalj v `meitationVduring'suchdisconnection;the system l, A can" be immediatelyi'put back in operation after 65 1' alternating currenti'b'y. means of electric current f inverters supplying; an alternating current gcir`M cuit Awhich is not supplied vbyany other type ci` converter,` the voltage wave .form and 'the' fre-` a-disturbance or a short circuit without the production of `undesirable current surges;` I t AIt lis, l therefore-:lone object)v of the' prsent input vcircuiti is "determined by frneans which re-I maintoperative during f temporary disconnection n j of `the inverting system from`ithesupply line. driving the motor is derived from the' converting f fue the motor thereby introducing a delay inith'e reaction oftliefsysftemQ-If means are providedm* Another 'object ,of the present invention 'is "ISA-5i" thevolta'ge wave ofl'the alternating current outn putv circuit is determinedf byrneansj` which are automatically provided with driving "means upon 80"E temporary 'disconnection of the inverting system.

l fromthe supply line. the control'fof thev rectifier.V When suchacon-f Another object pf the presenti "iriventipn is iwlrilflavide [a Control System ffor "ihirifig .SYS-x tems usingy electric current jrectiflers'jinf which Q85 the voltage Wave-of lthe*lalternali'),ing currentfouttornaticallyt disconnected from `*the output cir-"j Gumia y y, shortfcircuit in suchoutputcircuit.Y

age Wavegof the' alternating current output circuit isffdetrmndby means; which are'rnainteiedl ini 95" operating condition'duringtemporary disconnec#V tion f theinvertine system fromme vSnipiily?line kL by `rmeans utilizing'stored mechanicalvener'gy,

yfritlie, Object 0f the present invention: 1s 'to'` providel a' control system iorjinverting isystemsjloo using'l electric currentpgrectiflers 'iniwhich the t voltage Wave of thefalternatingxjcurrentjoutput y circuit is determined by meansj whichare"rnairl` .A tained f inV operating condition' 'during ntemporary disconnecticnof the invertingsystemgfrom the supply linebythe voltage `Wave determining means ofthe alternating'current output circuit ont' arit A y f other invertingsystem. put "in operation; the `terminalpvoltage of y the y, motoris below the necessary val'ueand connection Objects and advantages other than tirosealiover setrforth will be apparent fromthe 'following' occurrence of a 'disturbance or `of"` a description when read in connection with the accompanying drawings in which:

Fig. 1 diagrammatcally illustrates one embodiment of the present invention as applied to an inverting system in which the voltage wave determining means of the alternating current output circuit may be automatically disconnected from such circuit and which is provided with driving means upon occurrence of a disturbance in such circuit.

Fig. 2 diagrammatically illustrates a modification of a portion of the system shown in Fig. 1 in which the voltage `wave determining means of the alternating current output circuit are maintained at substantially operating speed by means of stored mechanical energy.

Fig. 3 diagrammatically illustrates a. further embodiment of the present invention as applied to two inverting systems each provided with means for determining the voltage wave of their respective alternating vcurrent output circuits inwhichrsuchmeans may be disconnected from the alternating circuit controlled thereby and may then be vmaintained in operative condition by the means associated with the other inverting system.

Referring 4more particularly to the drawings byA characters `of reference, reference numeral 6 designates a direct current supply line supplying current to be inverted into alternatingv current supplied to an output circuit7 represented as a three phase line in accordance with prevailing practice. The positive conductor of supply line 6 is connected with the neutral point of primary winding v8 oi a transformer having its secondary v,

winding 9 connected with line 7. The negative conductor of supply line 6 is connected with the cathode of a rectifier 12 of the metallic vapor arcing typeprovidedwith a plurality `of anodes 11 severally connected with the several phase portions of winding 8 and severally controlled by the actionof` a plurality of control electrodes 13. Eachcontrol electrode v13`is connected through aresistance 14 with one contact of a distributor 16operated by means of synchronous motor 17 `having itsarmature connected with line 7 and its fleld supplied `from a direct current source 18.

Each control electrode 13 is also connectedV through a resistance 19 with the negative terminal of a battery 21 having an intermediate point y thereof connected with the cathode of rectifier 12 and its positive terminal connected to the `brush of distributor 16. The voltage wave determining means `for the line 7 are here represented as consisting of a synchronous motor 22 provided with armature windings connected to line 7 through circuit breaker 29 and a field winding supplied from an`eXciter 23 mounted on the motor shaft. Exciter 23 is also utilized as a motor for the purpose o f'bringing motor 22 up to operating speed for which purpose exciter 23 is supplied from a battery `24 through a `switch 26. The system is connected with line 6 through a circuit breaker 27 provided with a tripcoil 28 connected in series with the tripcoil 31 of breaker 29 and with the vclosing coil 33 of a circuit breaker 32 connected in parallel with switch 26 and provided with a latch 34. The armatures 28,v 31 or 33 of the circuit breaker operating coils are energized `by means responsive to overloads in supply line 6 such as a shunt 36 in circuit in one of the conductors of said line.

When the system yis to be'brought into operating condition, supply linie 6 being. energized, closure of switch 26 will permit battery 24 to sup,-

Cf ply exciter 23 with` current* thereby permitting.`

exciter 23 to function as a motor to bring motor 22 to its normal operating speed and permits energization of the field windings of motor 22 from battery 24. Motor 17 is then energized from motor 22 .operating as a generator and rotates distributor 16 at a. speed synchronized with that of motor 22. By closing breaker 29, line 7 is energized at the voltage of motor 22 thereby energizing transformer windings 9 and 8 at operating voltages. Circuit breaker 27 may then be closed to connect line 6 with winding 8 and the system is connected foroperation as shown on the drawings. During the operation of the system each control electrode 13 .receives a negative potential from battery 21 through resistances 19 and 14, such potential being overcome once during each cycle of the voltage of line 7 by the positive voltage of battery 21 impressed thereon through one of the contacts of distributor 16. The several control electrodes 13 thus sequentially receive a positive potential impulse at the time when the associated anode 1'1 is positive with respect to the cathode of rectier 12.` Such condition prevails at the times when, the voltages of the portions of winding 8 connected. with the respective anodes are at a negative potential with respect to'the cathode of rectifier 12 and the potential is less negative than the potential of line 6 with respect to the cathode. Each anode 11 thus carries current for a fraction of a cycle and ceases to carry current whenthe potential of its associated winding portion 8 becomes less than the voltage of another windingy portion which then operatesA withl its associated anode.

Upon occurrence of a disturbance or of a short HU circuit in line 7., shunt 36 energizes cores 28, 31 and 32 at sumcientintensity `to produce opening of circuit breakers 27 and 29 and closure of circuit breaker 32 which is maintained in its closedposition by latch 34. Exciter 23 then operates yas a 115` motor to drive motor 22 at operating speed. so that, when the cause of disturbance zor the short circuit is removed from line7, the connections of the system may immediately be replaced in the position shown and the entire inverting system 12) may start to operate without any disturbance.

In Fig. 2, line 6, transformer 8, 9 and rectifier 12 Iwith its associated control are not shown, such elements being identical tothe elements shown in the embodiment of Fig. 1. Fig. 2 differs from that of breaker 32 is omitted and motor 22 is provided with a heavy fiywheel 37.. In the present embodiment the system is started as ldescribed above. relative to starting of the embodiment shown in Fig. 1 by closure of switch 26 followed by the closure of circuit breakers 29 and 27. The system operates as described above for Fig. 1 and upon occurrence of a disturbance, circuit breakers 27 and 29 are opened in response to current sup- Fig. 1 in that circuit connection of the system` from the supply line and from the output line, motor 22 continues to rotate by virtue of the inertia thereof and of flywheel 37 and, as it does not furnish `any energy to line 7, the speed of such motor will not differ greatly from the operating speed thereof at the time that the disturbance in the system has been removed and the system is reconnected for normal operation. Y

In the embodiment shown in Fig. 3, supply line 6 is connected with output line 7 through an inverting system identicalto that illustrated in Fig. 1 with the exception that circuit breaker 32 shown in Fig. 1 was omitted in Fig. 3. Line 6 is shown. 150.

The embodiment of 1215` motors to operating speed by means of va single' battery 24 with its associated switch 26 for oper ating exciter 23 and a second startingset such as` battery 24 with switch26are therefore not neces- 15 as supplying' current to asecond alternating current line 3inde'pendent' of line :'1 through an inverting system identicaltothe System supplying line '7 and not further identified by means of reference numerals with'the exception ofthe voltage wave determining rmeans forjline 38 which is 'represented as a synchronous motor v39. Motors 22 and 39` are mountedonthe same shaftfor simultaneous rotation thereof; 'Mechanical connection of motors-22 and 39 permits bringing both sary andare not showningthe system` supplying line38,r

-In operation, motors'22 and `,39 are'brought up to operating speed as described above in regard to yso lov

the embodiment of Fig. 1 and lines Tand 38 are supplied y with current, independentlyyof ,y each other, from their associatedinverting systems, the operation of each system being identical to that of the system shown,on-Fig.,1'.- Assuming-y that a disturbance or a short4 circuit occursin line 7, shunt 36Wil1 energize the armature'28 and,y

31 of the circuit breaker operating coils to trip rcircuit breakers 2'7Y and 29. VMotor 22V is then maintained at operating `speed andat operating voltage by meansvof motor 39 which is still enerf gized from line 38 which has not been effected by they disturbance occurring in line l'7. LWhen their disturbance has been removed, motor 2211s thus v in operating condition and circuit breakers'29 and 27y can be reclosed immediately thereby putting the system back intofoperation; l i

Although but a few embodiments of the present invention have been lillustrated anddescribed, it

r4will be apparent to those skilled'in the rart that various changes and ymodifications may be `made therein. without departing from the spirit'of the invention or from the scope of the appendedv claims.

. It is claimed and ydesired to secure by Letters Patent: f

1. In a system for inverting direct current into alternating current, `adirect current supply line, l an alternating currentdistribution line, an, elec- `tric valvel of the vapor arcing type connecting said f supplyline and said distribntionlinepmeans fory `former'having one winding connected withsaid vdlstnbutlon lme an 'electn Valve' of the Vapor" r'bution linsgelectric valves ofthe vapor ,arcing `arcing vtype connected with the other rwinding `of said transformer and with said supply line, means for vcontrolling the operation of said valve, a synchronous, motor connected 'with said distribution line to control the voltage wave shape therein,

means for bringing said motor up tooperating speed, means for automatically disconnecting said valve and said motor from said distribution/une upon theoccurrence of disturbancesfin said supply line, and means for retaining rsaidrnotor in "valve andsaid motor upon the occurrence of disoperative condition during"y the disconnection thereof.

3. In` a system lfor inverting direct current into alternating current, a direct current supply line,

van alternating current distribution line, a transformer-having one Winding-connected with said distributionline, anelectric valve of the vapor arcing type connected with the other winding of said transformer and with said supply line, meansl for controllingthe operation of said valve, a` syn`` Vchronous motor connected with said distribution line,l to control the voltage waveshape therein, means for bringing Vsaid motor up `to operating speed, acircuit breaker controlling the connection of .said valveV withl said supply line, and a circuit breakerv controlling` the connection of said motor with said distribution line, thevoperatingl 1 magnets of said circuit breaker being connected with said supply line ,and being lsimultaneously energized upon the occurrence of disturbances therein tooperatesaid circuit breakers. l

4. lIna ,system for inverting direct current into alternatingfcurrent, a direct current supplyfline, fan alternating current distributionline, a trans` former. having one winding connected with'said 100 distribution line, an electric `valve, of the vapor` arcing type connectedwith the otherv winding of 1 said'transforrner and with said supply line, meansv for controlling the operation of said valve, a synl chronous motor connected with said distribution line to control thevoltage wave shape therein,`

`means vfor bringingsaid motor up to operating speed,v a circuit breaker contro1ling the connection of said valve with saidV supply line, a circuit breaker controlling the connection of said motor with saidv distribution line,r`the operating magnets of said `circuit breaker-beingconnected withsad supply line and being simultaneously energized upon the occurrence of disturbances vtherein to operate said :circuit breakers,7 andmeans for retaining said motor in operativecondition during the disconnection thereof.`

5, Inra system for inverting Ldirect currentinto alternating current, a direct current vsupply line,`

an alternating current distribution line, a transformer having one windingconnected4 with said distributionline, an electric valveof the vapor arcing type connected 4withfthe other winding of said transformer and with said supply line, means for controlling the operation of rsaid valve," a synchronous motor connected with. said distribution means for bringing'said ,motor up to operating speed', means for automatically ldisconnecting said turbances in said supplylinef. anda flywheel drivline to control the voltage wave shape tlj1ereinY en bysaid motor for retaining Vthesame in operative 'condition during the disconnection thereof.

6.*In a system for inverting direct current into alternating current, a direct current supply line, a plurality of separate ,alternating current-distri# `bution lines, transformers each having one winding thereof severally connected with said distri-` type' severally :connected with the fother windings ofl said transformers and with said supply line,

for controlling the operations thereof, a syn- 14,0 means severallyassociated with each of said valves n chronous motor connected with each 'of said distribution lines `to control the voltage wave shape therein, said motors being Vmechanically 'connected, and means for vbringing. said motors up to operating speed. 1 f 

